since the last fillup i reset my odometer..yesterday while getting the low gas light i drove 15 minutes looking for a gas station by that time the needle was almost horizontal (olmost on zero) my odometer states 228 (all city driving mostly) and it allowed me to fill the car up to only 14.4 gallons (using 87 octane..I used 93 for 2 years but gas is expensive in NY now)

228/14.4 would make it approx 15.8 mpg
I did some research as seen below and the city mileage is supposed to be around 20. Plus the car should be able to go 342 miles on a tank of gas (city driving)

So the question is..why is it the gas light comes so early...does it leave an extra 3 gallons in the tank? since 17.1 gallons is the actual capacity...

and the second question is..why am i getting such horrible mileage I dont drive very aggresively either..and all this is with the AC off

please help me out...thanks in advance..

Fuel Tank Capacity: 17.1 gal.
EPA Mileage Estimates: (City/Highway)
Automatic: : 20 mpg / 28 mpg
Range in Miles: (City/Highway)
Automatic: 342 mi. / 478.8 mi.